Sounds like a good advice. I also have a family and very intensive primary job.

However, I would also like to renew math because of its general effects on the brain and because its hard. Without stressor, there is no improvement. I wanted a long time to devote few hours a week to study general math but if I can learn something that has usage in ML along the way, I consider it a double win.

For example, Fourier transformation and wavelates were very handy for me in understanding how certain DSP processes work while I had personal audio workstation and was doing digital composition most of my time.